Once a temperature sample has been taken and stored in the onboard
FRAM of the TV2 ThermaViewer
it can not be changed.

The time and temperature display parameters can be changed
if the user has the proper password, but the underlying data can not
be altered. It is stored in FRAM so even if power is lost the
data is protected. You can literally turn the TV2 off, run the
battery all the way down, walk away and come back 2 years later and
your data will still be there.

When the collected data is downloaded to a computer the TView program
displays it as a chart. Charts from multiple TV2s can be combined.
Data from one sensor can be moved to the chart of another sensor or
deleted from a chart or data from all sensors from one or more
sensors can be seen on one chart. Charts can also be printed out.

Additionally the charts can be exported to an XLS file which can be
viewed with Excel. If the data is saved rather then exported
it is saved as an encrypted file with a TXV file
extension, which can only be read or printed with the TView program.
If a previously saved 'txv' file is loaded into the TView program a
small icon appears on the screen indicating that you are viewing encrypted
data.

If exported data is loaded into Excel, Word, Notepad or some other
text editor type program it can be manipulated and re-saved but can
not be loaded into the TView program.
In other words it can be changed. Once this happens it no
longer meets the requirements of US regulation 21 CFR part 11.
As long is the data is in an TXV file it is encryped and complys
with the 21 CFR 11 requirements.